By Crispian Balmer and Selam Gebrekiden

ROME, June 12 (Reuters) - The slender Eritrean man with a close-cropped beard was arrested by Sudanese police on the afternoon of May 24 at a coffee shop in Khartoum. Two weeks later, he was flown to Italy in what Italian and British officials hailed as a rare blow against human trafficking.

They believed they had caught Medhanie Yehdego Mered, a ruthless kingpin known as "the General" in an illegal network that earned millions of dollars smuggling migrants by boat to Europe via Libya.

But friends and family say it is a case of mistaken identity. The man whisked to Rome on a special plane, they say, is impoverished 29-year-old refugee Medhanie Tesfamariam Berhe, a one-time carpenter with no criminal background, who was living quietly in Khartoum seeking to join his siblings in the United States when he was snatched from the Asmara Corner Cafe.

The man's Italian lawyer, Michele Calantropo, who met him for the first time in Rome on Friday, says his client is Berhe, not Mered, and he is innocent. He has requested his release from jail and a decision is expected this coming week.

Resolving the mystery is vital for both Italy and Britain. If they have the wrong man, it could be a huge blow in their battle against traffickers who have shipped more than 360,000 migrants to Italy across the Mediterranean Sea since 2014.

While Italy seeks to clarify his identity using voice recognition software, the British, who took the lead role in hunting him down, are insistent he is a trafficking figure. "We are confident in our intelligence," said an official at the National Crime Agency (NCA) in London.

Documents seen by Reuters and conversations with justice and security officials in both Italy and Britain show that the two countries have been working together since May 2015 to catch the General, using telephone intercepts to track his movements.

The last intercept came on May 23, placing him in Khartoum, said an Italian justice source who declined to be identified given the sensitivity of the investigation.

Sudanese authorities, who had met Italian and British officials in London earlier in the year to discuss the case, were given the details and the next day arrested the suspect.

The Sudanese declined any comment on their activities.

RANSACKED

Friends say six men in civilian clothes picked up Berhe at around 3.30 p.m. in the Corner Cafe, a small, rundown meeting place in Khartoum's Aldiem area which is frequented mainly by Eritreans and Ethiopians who plug into its Internet connection. Many patrons there said they knew Berhe.

"He came to this cafe every day to speak with friends and family," Asmerom, a 29-year-old Eritrean told Reuters outside the cafe. "I'm sure (Berhe) isn't the General. He is a very simple and poor guy," he said.

Samira Sallam, 24, who works at the restaurant, also said Berhe was "very poor".

"He used to come every morning to the café and order the cheapest breakfast we offer, which is just a falafel sandwich," said Sallam. "About a week or so ago, Sudanese security men came in civilian clothes and arrested him from inside the café�. The day of his arrest he did not pay for the meal he had."

Berhe shared two rooms with four other roommates including Ermiyas Kidane and a cousin, Temesgen Tesfay Haile.

Contacted by Reuters, the two men said Berhe did not have a job and depended on money from his seven siblings, six of whom are spread around the world, for living expenses.

That description of Berhe is at odds with the portrait of the General given by Italian authorities, who have charged Mered with human trafficking and abetting illegal immigration.

He faces up to 30 years in prison if convicted, and could also face possible murder charges linked to the sinkings of boats in the Mediterranean, where thousands of migrants have perished at sea crossing in unsafe boats.

Renato Cortese, head of the elite SCO police force, called Mered "the head of the situation room of a vast operation" of traffickers, often heard in tapped phone conversations arranging money transfers between various European countries.

Sicilian prosecutor Calogero Ferrara told Reuters Mered and another alleged kingpin purchased migrants from other criminals in Africa to send to Europe. Each boatload of 600 people would earn the smugglers between $800,000 and $1 million.

"ALL ERITREANS WANT TO LEAVE HOME"

One of Berhe's sisters, Seghen Tesfamariam Berhe, who lives in Khartoum, said that after his arrest he was brought back to his house by the security forces who ransacked the place, taking his documents and phone.

She said she had no idea why he was arrested. "That's the question I'm grappling with. I haven't found an answer."

Speaking to Reuters by telephone, Seghen said her brother had left Eritrea in October 2014, living with another sister in neighbouring Ethiopia before moving to Sudan in March last year.

Two other siblings live in San Francisco; one is in Angola and another in Norway. The parents and another sister remain in Eritrea.

Despite its tiny size, Eritrea, a horn of Africa nation along the Red Sea with only around 6 million people, has been the single largest source of sub-Saharan asylum seekers in the European Union for the past two years.

Last year, nearly 40,000 Eritreans made the perilous sea crossing to Italy across the Mediterranean, the single biggest group among the nearly 154,000 people who crossed. Almost as many came in 2014.

Most say they are fleeing political persecution in a country ruled by President Isais Afewerki for more than two decades with no opposition. All Eritrean men under 40 are subject to indefinite conscription into the army, where Human Rights Watch says they are often forced to work.

The country has had "no functioning legislature, independent press, or any semblance of civil society organisations" since a crackdown in 2001, and its people are subject to arbitrary arrest, disappearance and torture, the New York based rights group says.

"All Eritreans want to leave home because of the political situation there," Berhe's sister Hiwet told Reuters from Oslo.

Berhe's Facebook page is filled with videos about Barcelona soccer club as well as more personal messages. On Oct. 23, 2015 he posted a photo of the Eritrean capital: "I really miss Asmara," he wrote. There are also lots of posts about his Christian faith.

"God has the most amazing plan for you," says one entry dated Jan. 21, 2016 -- the day after sources say Italian and British investigators met to discuss how best to capture the General.

"CORRUPT CONTACTS"

In a letter summing up that meeting, which was seen by Reuters, the NCA said it was likely Mered was spending a "significant portion" of his time in Khartoum. It said it was confident Sudan would be willing to help, but saw some risks.

"There is good reason to suspect that (Mered) has corrupt relations in Sudan. However, the international high profile of this case may negate any attempt by (him) to use his corrupt contacts to avoid arrest," said the document.

The NCA declined comment on the letter or on the specifics of the operation to detain the suspect.

Rome does not have an extradition treaty with Sudan, so Italian officials met their Sudanese counterparts this year under the auspices of the NCA in London to pave the way for an eventual deportation.

No Italian judicial official was in Sudan for the May 24 arrest. An NCA officer was in Khartoum, an intelligence source said. The source did not say whether the British officer met the suspect or had access to him ahead of the extradition.

A judicial source in Italy said the first contact Italian authorities had with the suspect was when he was handed over to them at the airport in Khartoum for the flight to Rome on a private state jet.

The Arabic-language extradition document, seen by Reuters, was signed by the Sudanese justice minister. It states that the minister issued the order without any investigation by the Sudanese judiciary into the alleged crimes.

Italian magistrates in Sicily expect voice recognition tests will rapidly reveal if the man in custody is the person they overheard in numerous phone intercepts.

Sicilian magistrates also questioned him on Friday and said he had denied knowing the General. However, one of his 2,030 friends on Facebook is a woman called Lidya Tesfu, the wife of Mered, who lives with their child in Sweden. She did not immediately respond to a request for a comment.

An intelligence official, who declined to be identified, said it was conceivable that Mered was operating under an alias. He also said it was possible that in the end they would find out the man in custody was not the General.

"However, we do not think this man is the innocent victim that the media is portraying him to be. He is involved in the smuggling in some way or other," the source said.

Friends in Khartoum were convinced that Berhe would be vindicated and said he was due ample compensation.

"I sure he will become a rich man because of this mistake," said Andria Tasfai, 30, who used to hang out with him in the Corner Cafe. "I wish I had had his luck to get to Rome on a special plane," he added. (Additional reporting by Khalid Abdelaziz in Khartoum and Lin Noueihed in Cairo and Steve Scherer in Rome; editing by Peter Graff)